Internal combustion engines and other types of vehicle power plants produce various forms of vibrations which may be undesirably transmitted in any direction to the vehicle frame or other components if not properly dampened. These vibrations may be high or low in amplitude and high or low in frequency. Although many kinds of engine mounts have been devised in an effort to dampen various forms of such destructive or annoying vibrations and shocks generated by an engine to prevent them from reaching the vehicle frame, there remains a need for improved engine mounts or supports that are capable of damping a wide range of shock impulses or vibrations having both high and low amplitude vibrations as well as high or low frequency vibrations. Thus, such an engine mount should be capable of damping or absorbing the relatively continuous low amplitude vibrations and also cushioning against occasional high amplitude shock impulses.
In accordance with the present invention, a mounting device for resiliently attaching a vibrating body such as automotive engine to a frame or other vehicle member comprises first and second elastomeric support means having different damping characteristics, one of which resists transmission of relatively high amplitude vibrations and the other of which resists transmission of relatively low amplitude vibrations. Preferably, the first elastomeric support means interconnects a relatively rigid base member and a relatively rigid intermediate member and supports said intermediate member longitudinally, laterally, and vertically relative to the base member. Similarly, the second elastomeric support means interconnects the intermediate member with a suspended member and supports the suspended member longitudinally, laterally, and vertically relative to the intermediate member. In such an arrangement, the base member is adapted to be secured to a vehicle frame or the like, and the suspended member is adapted to be attached to the engine or other prime mover. The engine mount of the present invention thus functions to dampen various forms of engine vibrations in substantially any direction, thereby tending to isolate the vehicle therefrom. The properties of the engine mount according to the invention also lower the transmissibility of the engine vibrations both at resonant frequency and at higher frequencies, transmissibility being defined as the ratio of the output force of such vibrations exerted on the vehicle frame or other member to the input force exerted on the engine mount by the engine.
Additional advantages and features of the present invention will become apparent from the following description and the appended claims taken in conjunction with the accompanying drawings.